Serrated wave form generator



Dec. 6, 1938. H. o. ROOSENSTEIN 2,139,467

SERRATEDWAVE FORM GENERATOR,

Filed Oct. 30, 1936 INVE NTOR HAM/J 0- 2005576757 ATTORN EY Patented Dec. 6, 1938 SERRATED WAVE FORM GENERATOR Hans O. Roosenstein, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a corporation of Germany Application October 30, 1936, Serial No. 108,425 In Germany November 4, 1935 9 Claims.

This invention relates broadly to electrical apparatus for generating a wave of a saw-tooth or serrated wave form and more particularly to an Wave may be pi e-established and definitely controlled.

In the prior art it has been customary to generate a saw-tooth wave which is particularly adaptable for use with deflection apparatus in cathode ray tubes as particularly applied to their use in oscillographic or television arrangements. The common practice has been to linearly charge a condenser in one direction for the purpose of moving the cathode ray beam across a fluorescent screen to a definite point, and then rapidly discharging the condenser for the purpose of returning the beam rapidly to its initial point. The speed with which the beam was moved in either direction, that is to say, moving for the purposes of recording and return to the initial point, is dependent on the steepness of the wave front in each direction. It has been common practice to provide a discharge path which could be blocked until the condenser was charged and then rapidly unblocked forming a condition which approached a short circuit across the condenser. As a result it has been common practice to employ a thermionic tube for this purpose.

The unblocking of the discharge path has usually been occasioned by impulses received from the transmitter, termed synchronizing impulses, and these impulses are sent at the end of one line of scanning and also at the end of a complete frame of scanning and hence have been known by the terms line and frame synchronizing impulses. The prior art arrangements, as outlined above, have had the serious drawback when one or several of the aforementioned synchronizing impulses failed, the condenser voltage either exceeded or remained below the limits assigned to the highest and lowest desirable value of the.

saw-tooth curve, and following the reappearance of the impulses the charge on the condenser had not returned to its desired Value. Such complete failure, or distortion of the impulses, may occur not only on account of disturbances in television, for instance, but the circuit arrangement utilized for the production of the line deflection voltages, may be subject to spurious disturbances which tend to charge the condenser either past the limit desired or discharge it to a level lower than the lower level desired.

It is, therefore, the chief object of my invention to provide a control arrangement for the line or frame deflection generator in which the control is of such a nature that a smooth sawtooth shaped wave of predetermined upper and lower limits is definitely produced and maintained.

My invention will best be understood by reference to the accompanying figures in which:-

Figure 1 shows one embodiment of my invention.

Figure .2 shows another embodiment of my invention; and

Figures 3 and 4 are a set of explanatory curves.

Referring to Fig. 1, I is a thermionic discharge tube containing the usual control grid and anode and cathode and connected in parallel to the anode, cathode path is a condenser ll.

Joined in parallel with the condenser is a series circuit comprising a resistor l2 of comparatively high .value and plate potential supply l5. Joined in parallel also with the condenser are two rectifiers l3 and I4 respectively, one of whose electrodes may be joined to one terminal of the condenser directly and the other electrode in each case is joined to a portion of the plate potential supply l5 so that the rectifiers are biased by an amount as indicated as U1 and U2 in the figure. Both of these rectifiers are unidirectionally conducting devices and while the broad term rectifier has been used, it is understood, of course, that this term may embrace a common type of oxide rectifier or saturated diode or a tetrode or pentode, for instance.

Referring to Figure 2, a thermionic tube H1, in this case a triode, has joined in its plate circuit oppositely poled rectifiers H and I3. Also connected to the plate is a resistor l2 which has shunted thereto a condenser H, the terminal of the resistor opposite to that connected to the plate for the tube l0 being joined to the plate energizing battery l5. Also joined to thebattery !5. are the two rectifiers II and I3 which are shown as biased by voltages U3 and U4.

In Fig. 2, the position of the condenser II has been changed so that it is joined in parallel with resistor l2 rather than in series. The two biasing voltages for the rectifiers are indicated as U3 and U4 respectively and reference should be had to Figs. 3 and 4 for showing what these values indicate with respect to the upper and lower limits of the generated saw-tooth wave.

The action of the circuit is as follows. Assuming that the tube Ill be blocked, for instance, biased to a out 01f value, the condenser II will be linearly charged in accordance with the potential drop across the resistor l2 occasioned by the plate potential supply IS. The steepness of the wave front depends upon the value of the resistance l2 and the value of the condenser ll. Shortly before the value U2 (see Fig. 3) is attained, the tube I0 is rendered conducting by the arrival of a synchronizing impulse or other type of. voltage impulse supplied to the grid. I'he tube being conducting, the condenser will discharge through the tube due to the low internal resistance thereof and the speed of dis;

charge, which determines the steepness of, the

Wave front, will depend upon internal resistance of the tube at this time. Shortly before the voltage U1 is reached by the condenser discharging, the tube [0 is blockedagain so that an inner charging of the condenser takes place. Charging of the condenser H, in the case of; a

television arrangement correspondsito the duraticn of a line or frame and its discharge; corresponds to the time of the return stroke.

Now if a synchronizing impulse fails to arrive, due to fading, for instance, or spurious disturbances, the voltage value U2 to which the condenser is charged will be exceeded and the value of the triggering voltage across one of the rectifiers is exceeded and the rectifier becomes conducting, thus dissipating anyvoltage or current in excess of the value- U2 and hence limiting the upper limit of the curve to that value.

Similar action occurs if, owing to any disturbance, the tube In remains conducting too long so that the condenser would tend to discharge below the lower limit U1. In this case the rectifier I3 would become conducting and would build back up the charge on condenser H so that it was of a value equal to the triggering voltage on rectifier [3 which is selected as U1.

The curve illustrated in Fig. 4 shows the increase and decrease in the, charge and discharge pulses on condenser H when. the condenser is joined inparallel to the resistor l2, as shown in Fig. 2, rather than in series, as shown in Fig'. 1.

The action is the same in Fig. 2-as that shown in.

Fig. 1.

What I claim is:-

1. An apparatus for producing a serrated wave form comprising a condenser, means for linearly charging said condenser, a normally blocked discharge path for said condenser, means for unblocking said discharge path upon receipt of triggering impulses, and a plurality ofbiasedrectifiers connectedin parallel withsaid condenser.

2. An apparatus for producing aserrated wave form comprising a condenser, means for linearly charging said condenser, a normally blocked discharge path for said condenser comprising a thermionic discharge tube, means for unblocking said discharge path upon receipt of triggering impulses, anda plurality of biased rectifiersconnected in parallel with saidcondenser.

3. An apparatus for producing a serrated wave form comprising a condenser, means for linearly charging said condenser comprising a resistance and a source of voltage joined in series with said condenser, a normally blocked discharge path for said condenser, means for unblocking said discharge path upon receipt of triggering impulses, and a plurality of biased rectifiers connected in parallel with said condenser.

4. An, apparatus. for producing a serrated wave form comprising a, condenser, means for linearly charging said condenser comprising a resistance joined in parallel to said condenser and a source of voltage joined in series to the aforesaid parallel connection, a normally blocked discharge path for said condenser, means for unblocking said discharge path upon receipt of triggering impulses, and a plurality of biased rectifiers connected in parallel with said condenser.

5. In the method of developing serrated wave formations by charging and discharging a storage element the steps of controlling the maximum and minimum level of the stored energy comprising storing an electric charge of a value subject to exceed the pre-established maximum level, unilaterally conducting and dissipating the, charge exceeding said maximum level, discharging said stored energy, and unilaterally reinforcing said energy of discharge upon attainment of a value equal to the minimum level, in a direction. of conduction opposite to that of the, aforementioned unilateral conduction.

6. An apparatus for producing a serrated wave form comprising a condenser, means for linearly charging said condenser, a normally blocked discharge path for said condenser, means for unblocking said-discharge path upon receipt of triggering impulses, and a plurality of rectifiers connected in parallel with said condenser.

7. An apparatus for producing a serratediwave form comprising a condenser, means for linearly charging said condenser, a normally blocked discharge path for said condenser comprising a thermionic discharge tube, means for unblockingsaid discharge path upon receipt of triggering impulses, and a plurality of rectifiers connected in parallel with said condenser.

8. An apparatus for producing a serrated wave form comprising a condenser, means for linearly charging said condenser comprising a resistance and a source ofvoltage joined in series with said condenser; a normally blocked discharge path for said condenser, means for unblocking said discharge path upon receipt of triggering impulses, and a plurality of rectifiers connected in parallel with said condenser.

9; An apparatus for producing a serrated wave form comprising a condenser, means forlinearly charging said condenser comprising a resistance joined in parallel to said condenser and a source ofvoltage joined in series to the aforesaid parallel'connection, a normally blocked discharge-path for said condenser, means for unblockingsaid discharge path upon receipt of triggering impulses, and a plurality of rectifiers connected in parallel with said condenser HANS O. ROOSENSTEIN. 

